The present invention relates to a disc drive storage system. In particular, the present invention relates to an improved arm design having low mass and high stiffness for use in a disc drive system.
Disc drives are well known in the art and comprise several discs, each disc having several concentric data tracks for storing data. A transducing head carried by a slider is used to read from or write to a data track on the disc. The discs are mounted on a spindle motor which causes the discs to spin. As the discs are spun, the slider is positioned above a data track on the disc by moving an actuator arm on which the head is suspended. The actuator arm is moved using a large scale actuator motor, such as a voice coil motor. The time it takes for the actuator arm to position the slider at a selected data track is called the seek time.
In some applications, such as desk top computers, it is desired to minimize seek times as much as possible. In other applications, such as in lap top computers, it is desired to minimize energy consumption while still retaining a reasonable seek time. The energy required to position the slider at a selected data track depends in part on the mass of the actuator arm. Thus, one way to both improve seek times and minimize energy consumption is to reduce the mass of the actuator arm.
In addition, the mass of the actuator arm affects the ability of the slider to follow the surface of the disc. The actuator arm experiences certain resonance modes, which adversely affect the performance of the transducing head on the slider. To minimize the effects of resonance of the actuator arm, it is desired to keep the resonant frequency of the actuator arm relatively high. A high resonant frequency of the actuator arm results in lower resonant frequency amplitudes, which makes it easier to compensate for the resonant frequency using control algorithms incorporated into the control system used to position the slider.
Two factors which directly affect the resonant frequency of the actuator arm are the mass of the actuator arm and the stiffness of the actuator arm. To achieve the desired resonant frequency of the actuator arm, the mass must be minimized and the stiffness must be maximized. In other words, it is desired that the actuator arm be very lightweight, yet very stiff.
Currently, two methods are used in an attempt to increase the overall stiffness of the arms. The first method involves altering the geometrical features of a solid arm design. Current designs of actuator arms utilize an open cross section of material, such as a U-shaped beam, to form the actuator arm. The second is to tailor the stiffness of the arm by forming the arm from materials having a higher Young""s Modulus, such as A1, SS, or A1 Be. However, these attempts at improving the stiffness of the arm also tend to increase the mass of the arm, which in turn adversely affects the seek time of the disc drive and the resonance modes of the actuator arm.
Thus, there is a need in the art for actuator arms having increased stiffness, while keeping the mass of the actuator arm low.
The present invention is a unibody design for an actuator arm for use in a disc drive. The actuator arm is designed with a closed cross-section, allowing the actuator arm to be formed with a low mass, but high stiffness. To form the closed cross-section, the actuator arm is formed by a top skin and a bottom skin, with a core located between the top and bottom skins. The core serves to further stiffen the actuator arm, and may be formed of a variety of materials, including a corrugated metal, foam ceramic, foam metal, aluminum, a polymer, or even silicon. The skins may be affixed to the core, such as by adhesive or using spot welding depending on the materials used. A further benefit of forming the core from such materials is that the core then serves to reduce noise emissions and increase the dampening of the structure.